Ladder jack



R. L. SEARS June 20, 1967 LADDER JACK 2 Sheets-Sheet 1 Filed Jan.

R. L. SEARS LADDER JACK June 20, 1967 2 Sheets-Sheet Filed Jan. 5, 1966United States Patent 3,326,507 LADDER JACK Robert L. Sears, 2119 E. 9thSt., Des Moines, Iowa 50316 Filed Jan. 3, 1966, Ser. No. 518,407 9Claims. (Cl. 248-238) This invention relates to a ladder jack and inparticular to a scaffold support device for a ladder.

This invention relates to a scaffold support device which may be readilyattached and removed from a ladder as well as be moved to any pointalong the ladder as desired without removal of the device. As thescaffold support device is moved to different heights along the ladder ahook means engages the adjacent ladder rung. The pivotal movementpermitted and the shape of the hook means is such that the guide frameon which it is carried may be moved independently of the outer laddersection or with the outer ladder without interference from the rungs ofthe back ladder section. Moreover the hook means are adapted to engageonly the rungs of the outer ladder on which the guide frame is mountedregardless of their position between the top and bottom sides of theladder section. As the hook means moves up the ladder it is ratchetedover the rangs until the desired height is reached and then it ispermitted to drop back slightly whereby the hook means automaticallyengages the adjacent ladder rung. Furthermore, the center of gravity ofthe hook means is located such that the hook means will be pivoteddownwardly towards the rungs regardless of the angle between the ladderand the adjacent upstanding supporting surface. A stop means is providedto limit the pivotal movement towards and away from the rungs of theladder whereby the hook means cannot become engaged with the rungs ofthe bottom ladder or pivot too far outwardly to shift the center ofgravity to the opposite side of a vertical plane through the axis ofrotation for the hook means.

The guide frame is provided with side flanges which nest between theside rails of the outer ladder and thereby limit lateral movement of thescaffold support device. The scaffold support device may be mounted oneither the front or back side of the ladder as may be required.

One of the frame members of the scaffold support device is telescopinglyadjustable and includes a safety stop means which will preventaccidental disassembling of the scafi'old support device.

It is emphasized that the scaffold support device of this invention doesnot in any way interfere with the use or operation of the conventionalsingle unit ladder or extension-type ladder.

This invention consists in the construction, arrangements, andcombination of the various parts of the device, whereby the purposescontemplated are attained as hereinafter more fully set forth,specifically pointed out in the claims, and illustrated in theaccompanying drawings,

in which:

FIG. 1 is a fragmentary perspective view of a ladder with the ladderjack mounted thereon;

FIG. 2 is an exploded view of the ladder jack;

FIG. 3 is a fragmentary side elevation view taken along line 3-3 in FIG.2 showing in particular the extendable frame member;

FIG. 4 is a cross-sectional view taken along line 44 in FIG. 3;

FIG. 5 is a side elevation view of the jack device mounted on theopposite side of the ladder from its position as shown in FIG. 1;

FIG. 6 is a fragmentary cross-sectional view taken along line 66 in FIG.7;

FIG. 7 is a fragmentary top plan view of the jack device mounted onextension ladders; and

3,326,597 Patented June 20, 1967 FIG. 8 is a fragmentary cross-sectionalview enlarged to show the various positions of ladder rungs andpositions to which the hook means may be pivoted.

The ladder jack device of this invention is referred to generally inFIG. 1 by the reference numeral 10 and is shown mounted on a ladder 12having extendable sections 14 and 16.

The ladder jack, as shown in FIG. 1 is mounted on the back side of theladder 12 and includes basically three main components, a guide frame 18and a pair of support frames 20 and 22. As seen in FIG. 1, the guideframe 18 is hooked to the ladder 16 and the support frame 20 isextendable. All of the three main components are pivotallyinterconnected to form a generally triangular shaped device.

The guide frame 18 is generally rectangular in shape having a pair oflongitudinal L-shaped in cross-section side members 24 interconnected bytransversely disposed end square in cross-section members 26 and 28. Aleg 25 (FIG. 6) on each side member extends between the side rails ofthe ladder 14 to limit lateral movement of the guide frame 18. Each ofthe end members 26 and 28 are hollow to receive connecting pins 30 and32. The side members 24 are spaced apart a distance substantially equalto the width of the ladder while the transversely extending members 26and 28 have outwardly extending end portions 34 and 36 which extendoutwardly of the side members 24 and the sides of the ladder 12.

Adjacent the end member 28, is a transversely extending rocker shaft 38with its ends rotatably mounted in the side frame members 24. A pair ofbook members 40 of plate material are rigidly connected to the rockershaft 38 closely adjacent the side frame members 24 and a handle 42 ispositioned between the hook members 40 for manually rotating the hookmembers 40 out of engagement with ladder rungs 44 as seen in FIG. 1.

Each of the hook members 40 as seen best in FIGS. 6 and 7 has arelatively long throat portion 45 with its free end rigidly connected tothe rocker shaft 38 which is adapted to rotate relative to the sideguide frame members 24. The inside edge 46 of the hook 40 is parallel tothe outside edge for a substantial distance and then diverges therefromto form a concave edge 48 which terminates in a concave edge 49 with arelatively smaller radius of curvature for matingly engaging the rungs44 of the ladder section 14. The forward edge of the hook 40 is convexat 49A along its entire length. A small finger 49B bridges the edgesurface of the hook 40 between the convex outer edge surface 49A and theinner concave edge 49.

Normally the weight of the hooks 40 is sufiicient to cause them to pivotdownwardly for engagement with the ladder rungs 44 but if desired aballast element 49C may be added to the handle 42 to accelerate thismovement.

The books 40 are limited in their pivotal movement in both directions bystop elements 49D on the side members 24 of the guide frame 18. The stopelements are positioned to prevent inward movement of the hooks beyondthat illustrated in the innermost position in FIG. 8 therebypreventing'engagement with the rungs of the bottom ladder 16. In thiscase the stop element 49D engages the top edge of the hook rearwardly ofits pivotal axis and in limiting outward pivotal movement it engages thehook element forwardly of the pivotal axis. In the latter case the hookis prevented from pivoting so far out that the center of gravity isshifted to the opposite side of a vertical plane through the hookspivotal axis.

When the ladder jack is mounted on the ladder 12 as shown in FIG. 5, thesupport frame 20 is oriented with a channel or yoke shaped end 50extending downwardly 0 wherein side plate flanges 52 are aligned to beconnected by the pin 30 to the guide end frame member 26. The

channel-shaped end 50 includes a transversely extending base portion 54having an extendable pair of L-shaped sections 56 and 58 connected atits center. The L-shaped sections 56 and 58 nest in each other and arelocked together by a pin 60 extending through aligned openings '62. Apair of U-shaped glide elements 64 and 66 are rigidly secured to theouter surface of the member 58 to hold in mating engagement adjacentlegs of the extendable members as seen in FIG. 4. The guide element 60is placed at the very end of the extendable member 58. A stop element70is positioned between the legs of the member 56 anddisposed along itslength between the guide elements 64 and 66. Thereby, the extendableelements 56 and 58 may move in either direction until the stop element.70 engages one of the guide elements 64 or 66. Thus, if the pin 60 everis accidentally removed, the extendable elements 56 and 58 will notseparate or be completely contracted.

The support frame member 22 also has a channelshaped end 72 (FIG. 2)with side plate flanges 74 and a base element 76. As seen in FIG. 5, theflange plate elements 74 are adapted to embrace the ladder 16 and bealigned with the opening through the end member 28 of the guide frame 18for interconnection by the pin 32. As seen in FIG. 5, a second pin 78 isemployed on the opposite side of the ladder 16 from the pin 32 therebygiving extra assurance that the jack device will not pivot outwardlyfrom the ladder as viewed in FIG. 5. The ends of the support framesections 20 and 22 opposite the channel ends 50 and 72 respectively, arepivotally interconnected at 80. Thus, a support surface is provided bythe support frame section 22 for scaffolding material 82 as seen in FIG.5.

As seen in FIG. 1, the jack device is mounted on the side of the ladderfacing the vertical support surface such as a wall. Consequently, theextendable support frame section 20 is as shown, turned end for endrelative to its position in FIG. and rotated 180 degrees from itsposition in FIG. 2. The scaffolding material would of course be placedon the support frame section 22.

In operation it is thus seen that the guide frame 18 with the hooks 4i)engaging the rungs 44 of the ladder 16 is always positioned on the outerside of tthe ladder whether the jack device is mounted on the inside ofthe ladder as seen in FIG. 1 or on the outside as shown in FIG. 5. Inconverting from one position to the other it is only necessary to removethe pins 30, 32 and 78. The pin 78 is not necessary in positioning thejack device on the inside of the ladder as seen in FIG. 1. Depending onthe angle at which the ladder rests against a vertical wall or the like,the support frame will be extended or contracted by moving the pin 60 tothe appropriate aligned openings in the extendable sections 56 and 58.The adjustment is made to position the support frame 22 in a horizontalplane to receive the scaffolding material 82.

In moving the jack device up the ladder the hooks 40 ratchet over therungs 44. It is seen from FIG. 8 that regardless of where the rungs areplaced relative to the top and bottom sides of the ladder section asseen by rungs 44, 44A, 44B, 44C and 44D, the forward convex edge 49A ofthe hooks will contact and slide over the rungs around the finger 49Bwhereupon the selected rung will be nested in mating engagement with theconcave edge 49. Where the rungs are placed close together such as rungs44 and 44A, the top rung 44A may still engage the concave edge 49because the long narrow throat portion 45 is spaced above the lower rung44. When a rung engages the throat 45 will automatically guide the runginto the hook edge 49 as the guide frame is lowered. By employing thenarrow finger 49B and placing the rung engaging edge 49 closely adjacentthereto, there is maximum clearance between the finger 49B and the rungsof the lower ladder section 16 even if they are located close to the topside of that ladder section.

When the jack device is to be lowered, the handle 42 is used and pivotedoutwardly against the action of gravity tending to pivot it intoengagement with the rungs of the ladder 14. This results in an importantsafety feature since if control of the jack device is lost it cannotdrop to the ground because the hooks 40 will automatically pivotinwardly into engagement with the next lower rung 44;

Also safety is provided in the frames 20 and 22 as they cannotaccidentally come apart when the telescoping adjustment is being madebetween members 56 and 58.

Some changes maybe made in the construction and arrangement of my ladderjack without departing from the real spirit and purpose of my invention,and it is my intention to cover by my claims, any modified forms ofstructure or use of mechanical equivalents which may be reasonablyincluded within their scope.

I claim:

1. In a ladder jack device,

a guide frame adapted to detachably engage the rails of a ladder forlongitudinal movement therewith, hook means on said guide frame fordetachably engaging the rungs of a ladder that extend between said Iladder rails,

a first scaifold support frame pivotally secured to said guide frame andextending outwardly therefrom,

a second scaffold support frame pivotally secured to said guide frameand extending outwardly therefrom,

said first and second support frame pivotally and detachably securedtogether to form a horizontal scaffold support,

each of said support frames has a channel-shaped portion on one end,said chanel-shaped portions adapted to receive a ladder, said guideframe being pivotally secured between the outer ends of the channelportions of said support frame, said guide frame being rectangular inshape with transverse end portions having an opening formedtherethrough,

and a detachable rod extending through the ends of said channel portionsand the opening in the adjacent guide frame end portion.

2. The structure of claim 1 wherein one of said scaffold support framesincludes and is formed by a pair of interconnected extendable members, alock means for selectively locking said extendable members together at apredetermined length and a stop means to limit the extension of saidmembers upon removal of said lock means.-

3. The structure of claim 2 wherein one of said extendable membersincludes a pair of guide elements slidably engaging said otherextendable member, said stop means is secured to said other extendablemember and positioned between said guide elements, one-of said guideverse cross-section and disposed in nesting relationship,

said guide elements being secured to the outer surface of said onemember and having a U-shaped outer end portion matingly engaging a pairof adjacent leg portions.

4. The structure of claim *1 and one of said channelshaped end portionshas a second rod extending through the ends of said chanel portion andadapted to be disposed on the opposite side of a ladder from the firstmentioned adjacent rod.

5. The structure of claim 1 wherein the transverse end portions of saidguide frame extend outwardly of each side of the side portions of saidguide frame and are adapted to terminate outwardly of the longitudinalside edges of a ladder for engagement with the flanges of said channelend portions on said support frame members, the side portions of saidguide frame being L- shaped in cross-section with one leg of each sideportion adapted to engage the inner side of an adjacent ladder rail tolimit lateral movement of said guide frame.

6. The structure of claim 1 and said guide frame has a pair oflongitudinally extending side portions, and a rod rotatably extendsbetween the opposite longitudinal side portions, said hook meansincluding a pair of hook members rigidly secured to said rod adjacentand between the sides of said guide frame for pivotal movement into andout of engagement with the rungs of a ladder.

7. The structure of claim 6 wherein said hook members have a center ofgravity which tends to pivot said hook members downwardly between saidside portions when said guide frame is disposed with an angle of lessthan 90 degrees between the underside of said guide frame and thehorizontal.

8. The structure of claim 7 and stop means is provided to limit theinward pivotal movement of said hook means from moving beyond thesubstantial thickness of an outer ladder section in an extendable ladderand limit the outer pivotal movement from shifting the center of gravityto the opposite side of a vertical plane through the axis of rotationfor said hook means.

9. The structure of claim 8 wherein said members each have an elongatedthroat portion connected adjacent its free end to said rod, said throatportion having a substantially straight inner edge extending from saidpivotal axis and merging into a first concave edge portion and then intoa second concave edge portion at the outer end of said hook, said secondconcave edge portion having a smaller radius of curvature relative tosaid; first concave edge portion and adapted to matingly ena gage therung of a ladder, said second concave edge portion forming one edge of arounded narrow finger portion and a convex edge forming the oppositeside of said finger portion, said convex edge portion adapted to contactthe rung of a ladder and slide said hook over said rung, said convexedge tapering from its outer most end remote from said finger portioninwardly towards said axis of rotation of said hook portion.

References Cited UNITED STATES PATENTS 161,010 3/1875 Davis 182-210441,722 12/1890 Vassall 182-117 754,427 3/ 1904 Copeman 248238 1,332,3853/ 1920 Dunlap 248238 FOREIGN PATENTS 5,602 6/ 1932 Australia. 29,43310/ 1930 Australia.

REINALDO P. MACHADO, Primary Examiner.

1. IN A LADDER JACK DEVICE, A GUIDE FRAME ADAPTED TO DETACHABLY ENGAGETHE RAILS OF A LADDER FOR LONGITUDINAL MOVEMENT THEREWITH, HOOK MEANS ONSAID GUIDE FRAME FOR DETACHABLY ENGAGING THE RUNGS OF A LADDER THATEXTEND BETWEEN SAID LADDER RAILS, A FIRST SCAFFOLD SUPPORT FRAMEPIVOTALLY SECURED TO SAID GUIDE FRAME AND EXTENDING OUTWARDLY THEREFROM,A SECOND SCAFFOLD SUPPORT FRAME PIVOTALLY SECURED TO SAID GUIDE FRAMEAND EXTENDING OUTWARDLY THEREFROM, SAID FIRST AND SECOND SUPPORT FRAMEPIVOTALLY AND DETACHABLY SECURED TOGETHER TO FORM A HORIZONTAL SCAFFOLDSUPPORT,